Validity of Axial Length Measurements for Monitoring Myopic Progression in Orthokeratology

PURPOSE. To investigate the short-term effect of orthokeratology (ortho-k) lens wear on the anterior segment length for validating the use of axial length for monitoring myopic progression after ortho-k treatment. METHODS. Thirty-seven and 39 subjects (ages: 7-10 years) were randomly assigned to wear ortho-k and single-vision spectacles, respectively. Central corneal thickness (CCT), anterior chamber depth (ACD), crystalline lens thickness (LT), and anterior segment length (ASL: summation of CCT, ACD, and LT) were measured before and 6 months after the treatment under cycloplegia. Changes in these parameters were evaluated and compared between the two groups of subjects. RESULTS. There were no significant between-group differences in the baseline data (P > 0.37). After 6 months of lens wear, in the ortho-k group, CCT was significantly reduced by 0.009 +/- 6 0.009 mm (P < 0.001), whereas ACD and LT remained unchanged (P > 0.15). In the spectacle group, ACD was significantly increased by 0.01 +/- 0.03 mm (P = 0.008), whereas CCT and LT remained unchanged (P > 0.06). In both groups of subjects, ASL did not appreciably change but axial length was significantly increased by 0.10 +/- 0.10 mm and 0.20 +/- 0.11 mm in the ortho-k and the spectacle groups, respectively (P < 0.001). CONCLUSIONS. Eyeball elongation occurred in children wearing both ortho-k and single-vision spectacles. Since ASL was not affected by ortho-k treatment, axial length measured reflects the true growth of the eyeball and is a valid parameter for monitoring myopic progression in ortho-k treated eyes. (ClinicalTrials.gov number, NCT00962208.) (Invest Ophthalmol Vis Sci. 2013;54:1613-1615) DOI:10.1167/iovs.12-10434